Ore pelletization process and products



United States Patent 3,266,887 ORE PELLETTZATEGN PROCES AND PRODUCTSWalter E. Kramer, Niles, and Louis A. Goretta, Naperville, lll.,assignors to Nalco Chemical (lompany, Chlcago, Ill., a corporation ofDelaware No Drawing. Filed Oct. 29, 1962, Ser. No. 233,948 19 Claims.Il. 75-3) This invention relates to an improved method for pelletizingmetallic minerals and ores, resulting in pellets having increasedstrength and cohesiveness. More particularly, this invention isconcerned with the use of amine humate salts as pelletizing aids in sucha process, which salt inclusion aids to increase the overall efficiencyof the pelletizing process and also produce pellets of such increasedstrength, cohesiveness etc., that they are attrition resistant and ableto withstand mechanical and thermal shock.

In recent years, the metal refining industry has undergone strikingchanges in processing ores for refinery and/ or smelting. In particular,emphasis has been placed upon production of pellets making a part or allof the ore charge since their use has resulted in immense increases inefficiency in operation of blast furnaces. In particular, the melting ofsuch pellets in a blast furnace can be achieved at increased rates, withconcurrent decrease in emission of small particles of flue dust whichfor most eflicient operation must be collected and reused. Also, apermeable bed of pellets allows rapid transfer of the hot reducing gasesthrough its entire dimension. In many instances up to 20% increases inefficiency have been noted when ore pellets are used in the blastfurnace. The reduction of iron ore and manufacture of steel areparticularly improved through use of such pellets.

While in some instances relatively pure ores containing a highpercentage of the valuable mineral constituent have been pelletizedafter minor prior processing such as crushing, of more importance is theproduction of pellets from relatively impure ores, such as ores having alow content of iron oxide. Since these ores of necessity must bebeneficiated, that is, increased in relative proportion of desired metalcontent, and since after such process of beneficiation the purifiedmineral is already in the wetted particulate state, a pelletizationprocess is particularly suitable. The ore mass then can be easily andconveniently made into pellets for subsequent blast furnace use. Also,not only are the lower grade ore deposits such as finely dividedhematite iron ore deposits more useful in such pelletizing process, butalso tai-lings from prior ore processing, which have heretofore beendiscarded and stockpiled, can also be made into convenient pellet size.Thus, in the case of these relatively impure minerals or byproductfines, not only is it desirable to pelletize these materials, but inmany instances it is also essential. For example, in the case of workinglow grade iron ores the products cannot be fed directly into a blastfurnace due to the fact that the high content of impure materials wouldcause considerable slag with result of inefiiciency of operation andrepeated breakdown. Likewise, many of these relatively impure oredeposits are in such a fine state of aggregation that they would be lostthrough the flue of the blast furnace long before any liquification intoa fluid state could take place. The same result occurs through use offlue dust, which, while it could be collected and reused, neverthelessin subsequent reuse without further processing would again be lostthrough the flue. Therefore, these fine particles must be processed intolarger dense masses such as small integral units or pellets. Thus, itcan be seen that the pelletizing process is admirably suited to use ofthe above type materials.

As is mentioned above, in the case of impure mineral deposits the valuedor desired metal constituent in the 3,266,887 Patented August 16, 1966"ice mineral must be concentrated prior to pelletization. For example,many impure iron ore deposits have an iron content as low as 30% orless. These deposits must be increased in iron content to above about60% in order for them to be economically and efficiently employed in theblast furnace as pellets.

In general, these impure ore deposits are processed to the desiredwetted particulate state prior to pelletization as follows: The firststep normally involves crushing or comminution of the raw ore as minedor in the presence of a liquid media, most generally water, by means ofsuccessive reduction steps to the final particulate stage. In thecrushing operation in which the final particles are usually ground to afine or intermediate state, two general types of mechanisms are employedto apply gradual pressure to the particles. The first mechanism involvesreciprocating breakers, that is, alternate approach and withdrawal ofthe crushing surfaces in the crushing zone to a substantially fixedpredetermined minimum spacing. Reciprocating pressure breakers includesuch mechanisms as jaw, gyratory, cone and gyrasphere crushers. Thecontinuous pressure breakers include rolls, single roll crushers androller mills. Of lesser importance are impact crushers such as stamps,hammer mills and tumbling mills.

In order to concentrate the valuable or desired metal in the mineral,now in a particulate state, it is necessary to separate it from theimpurities or gangue which normally contains a substantial amount ofsilica which is later discarded. One means by which the mineral may beseparated from the gangue is by gravity concentration since the desiredmetal portion of the mineral and gangue differ appreciably in specificgravity. The theory or gravity separation depends upon a difference inmovement in response to joint simultaneous actions upon the mineral andimpurity or gangue by gravity and one or more other forces. This typeconcentration may be carried out by means of pulsated, shaken, orstirred beds, water impulse separators, pneumatic concentration, etc.Normally, water is employed as the impregnating fluid. Another method ofconcentration of the valuable mineral constituent is by means offlotation processes. Normally these consist either of froth flotation oragglomerate or table flotation. Another excellent method ofconcentrating the desired constituent is by magnetic means. This iseffective only with magnetic iron oxide ores. In particular, magneticiron ores such as taconite are admirably suited to beneficiating bytreatment of the ores with electromagnets or magnets.

After the desired mineral content has been increased to a relativelyhigh content via any of the above means, the material must normally bepartially dewatered either by draining or thickening. For best pelletformation the mass of the particulate mineral substance to be processedmust be in a damp or wetted condition. Normally from 510% by weight ofwater content is required for eflicient pellet formation. In conjunctionwith the dewatering process, normally the beneficiated ore must befiltered to give a wet ore mass having water in the above range. Thisfiltration may be carried out by use of continuous vacuum, sand,pressure, vacuum-leaf, centrifugal, etc., filters. After suchprocessing, the mineral is now in the desired state for pelletformation.

The concentrated, dewatered ore may be pelletized alone or flue dust maybe added thereto and the resultant mixture pelletized. Likewise moistflue dust may be pelletized singly. Generally, prior to the pelletforming-step, coke is added as a fuel media for use in the subsequentstep of firing or setting the formed pellets to a hard mass suitable formechanical handling and shipping. Normally since the bulk of thesiliceous material has been removed in the separation of the gangue fromvaluable mineral constituent, no flux is necessary. However, in someinstances a small amount of calcium carbonate-containing material,preferably limestone, may be used as a flux. This flux intermingle inthe pellet causes ore such as iron ore to melt more readily bydissolving the outside or surface impurities, thereby increasing thefluidity of the impure ore in bringing all of its components to a moreintimate contact during the liquification step at the blast furnace.

In addition to sources of ore such as the low grade ores which have beenprocessed as generally outlined above, ore flue dust or sludges may alsobe used. In the case of iron ore a convenient source is found in the useof sludge which is obtained in aqueous suspension or slurry, from fluegases which have been collected from blast furnace stacks, wetted in gaswashers and then concentrated. Other iron ore sludges may be found, forexample, in holds of iron ore barges or around iron ore shiploadingareas. Also, in addition to use of flue dust as a by-product from theblast furnace melting process, cold and hot fines falling from a sinterprocess, and tailings from other iron ore processing may be used. Forconvenience sake these finely divided dry iron materials, generally inthe form of impure iron oxides, may be referred to as iron dust. Again,these may be used alone, in combination with each other or with thebeneficiated ore concentrate and/or the ore sludge.

In order to form an ore pellet of sutficient strength to hold its shapeprior to the firing step, it is necessary, as mentioned above, that itcontain suflicient water to form a damp mass suitable for formation of acohesive pellet. Normally in the case of impure ore deposits which havebeen processed by the above stated steps, suflicient water remains afterthe filtration step so that no additional water need be added. In somecases though, it may be necessary that water be added to the material tobe pelletized in order to give it more compactness in pellet-formingtendency. The water may be added directly to the material at any pointprior to the pelletizing, and/ or it may be introduced into the systemby use of ore sludge. A burden form material to be pelletized is thenavailable in a form for ready pelletization by means of known machinery.

The pelletization step itself may be carried out by such machinery as adisc or drum pelletizer. This machinery comprises a rotating inclinedsurface which agglomerates the burden material composite into pelletswhen the burden is flowed upon the revolving inclined surface. Theburden therefore must be capable of being compacted into pellets byvirtue of the centrifugal force imparted by the revolving pelletizers.Therefore, it is essential that the burden have sufiicient adhesivequalities in order to form relatively large pellets of sufiicientstrength to withstand subsequent processing and transfer prior to theirfiring. Multiple-cone drum pel-letizers are particularly desirable forthe pelletizing operation. Another type of machinery available for thisuse is a pug mill which in its simplest form is a long trough containingtwo parallel counterrotating paddle-bearing shafts, horizontally mountedin side by side relationship so that the paddles on respective shaftsare moving upwardly and away from each other in the center of thetrough. This paddle action tends to fluff the burden mix, and cause thedampened mass to be joined into cohesive particles. It is essential tothe pelletizing process that the core either have some inherent naturalbinding tendency or be treated so that its binding tendency is increasedto the point where pellets may actually be formed. Ores containing clayimpurities have such natural binding tendency. However, these ores arebecoming increasingly scarce and the harder to handle ore such as ironores of relatively low iron content are becoming increasingly moreimportant.

Therefore in order to give compression or green strength to the pelletswith concomitant increase in pellet size, it has been proposed thatsubstances be introduced into the burden material in order to act asbinders both during the pelletizing step and subsequent thereto. Prior 4art substances such as pickle liquor, lime, starch and other naturallyoccurring organic materials, and the like have been tried with littlesuccess. These prior art binders either fail to impart the requiredgreen strength to the pellets or commonly fail to increase the pelletsize to that suflicient for efiicient utilization in the firing processand subsquent blast furnace operation. Many of these substances give abarely passable pellet only with increased retention time in thepelletizing process, thus increasing cost by reducing through-put.

Another material which has been used as a binder is bentonite, .anaturally-occurring clay. However, this material has the importantdisadvantage of adding silica to the burden mixture. To combat thisproblem, additional amounts of limestone are required to remove thesilica contained in the bentonite during the blast furnace operation.This silica creates large amounts of unusable and deleterious slag inthe blast furnace operation. Another disadvantage of such material isthat relatively large quantities must be used to give the requiredbinding effects.

It would therefore be an advantage to the art if a binder could beintroduced into burden material which is to be pelletized, which binderwould increase the pellet size of the burden, allow a rapidpelletization, and increase the green" or compression strength of theformed pellets, thereby allowing considerable physical handling withoutbreakdown in pellet size or shape. Another advantage would be realizedif this binder was relatively inexpensive, imparting no deleteriousimpurities into the burden and resultant fired pellet product, and coulditself be used as a source of fuel during the firing where the formedpellet is fixed into a hardened state.

It therefore becomes an object of the invention to provide a method ofincreasing efficiency of pelletizing metallic minerals and improving thepellet product thereof by addition of a novel binder into the ore burdenprior to its pelletization.

Another object is to provide an organic binder of a relativelyinexpensive nature, which can be efliciently fed in low amounts into amineral burden without introducing impurities which would adverselyaffect the subsequent process of firing or the use of resultant productsthereof as a blast furnace feed.

Another object of the invention is to provide ore pellets, andparticularly iron ore pellets having improved green strength and abilityto withstand considerable handling prior to their firing and fusing, thethermal shock during such firing.

Another object of the invention salts which may be used as and relatedprocess.

In accordance with the invention, it has been found that certain novelorganic salts comprising amine humate salts are extremely useful asbinders for metallic mineral ore pellets. Use of such salts as bindersincreases the ability of ore composites to be pelletized into relativelylarge pellet sizes, with the resultant pellets having sufficientcompression or green strength to withstand handling and transferringprior to their firing to a fused mass. Generally speaking, the processof the invention comprises addition of at least a binding amount ofamine humate salt to a wetted mass of comminuted metallic mineralwhereby a composite is formed and then pelletizing the composite intointegral units or pellets.

The processing of impure mineral ores into their final hardened pelletstage generally includes the step of comminution of a mineral ore toparticulate size, concentrating from this impure ore the valued ordesired mineral constituent thereof to any desired increased purity bytreating the mineral such as by gravity concentration, flotation, ormagnetic separation, etc., in order to obtain a wetted particulate mass,pelletizing this wetted mass into intregal or individual pellets andfinally firing the formed pellet units to a hardened fused state for usein blast furnace operations. The particular improvement is to provideorganic pelletizing aids in ore refining in this method, comprising theinvention, is addition of an amine humate salt during or before thepelletization step whereby pellets are easily and efficiently formed dueto the binding effect of the humate salt to a point where they havesuflicient strength and adhesiveness to withstand the mechanicalhandling, prior to firing and the thermal shock during the actual fusionof the bound pellets.

Almost any type of metallic mineral desired to be pelletized mayadvantageously be acted upon by the amine humate salt binders. Forexample, the predominant desired metal constituent of the mineral may bechosen from among lead, copper, nickel, zinc, uranium, iron, etc.Mixtures of the above or any other metal occurring in the free ormolecularly combined natural state as a mineral, or any combination ofthe above, or other metals which are capable of pelletization may beacted upon by the amine humate salts. While particularly effectiveresults are realized in pelletization of minerals predominantlycontaining iron, it is understood of course that the inventionencompasses enhancing the binding into pellets of any mineral containinga variety of metals or containing a single constituent in highabundance. For purpose of simplicity, the following discussion relatingin more specific detail the peil-etization process of the invention willbe limited to process ng of iron ores. It is understood that this ismerely illustrative and the invention cannot be considered to be limitedthereto.

As mentioned above, the burden or material to be pelletized may containiron ore deposits coming directly from the mining site, from oretailings, flue dust, cold and hot fines from a sinter process or ironore which may be found in a sludge condition as aqueous iron oreconcentrates from natural sources or recovered from various processes.For example, flue gases containing fine flue dust particles may becaught, wetted in gas washers and then concentrated by coagulation-typeclaritiers into a relatively concentrated wet sludge which may beemployed in the pelletizing operation. Any one of these sources of ironor any possible combination thereof may be employed according to theiravailability and particular process setup of the pelletizing unit,normally existing at the mine site itself. Iron ore or any of a widevariety of the following minerals may form a part of the burden:magnetite, hematite, limonite, goethite, siderite, franklinite,ilmenite, chromite, pyrrhotite, cholcopyrite, pyrite, etc.

To the burden may be added a flux material chosen from a number ofsubstances. In most cases due to the fact that silica and relatedimpurities have been re moved in the processing prior to pelletization,a flux material is not needed. However, if such is necessary, a calciumcarbonate containing substance is generally employed because ofavailability and relatively low cost. Among these, limestone or animpure source of limestone, such as calcite are suitable. Calcite isalso known as calcspar which is a hexagonal, normally colorless,rockforming mineral composed of both crystalline species, such asIceland spar, corn spar and satin spar, and amorphous varities includingchalk, marble, limestone, stalactite and baryte. Also spongy andflake-like calciumcontaining mineral forms, such as mountain milk andschifer spar may be employed.

Another element in the burden, normally essential in order to fire andfuse the formed burden pellets after pelletization, is a source of fuel.Generally coke is employed, but any other inexpensive source of fuel maybe included in the operation. A particular advantage in the use of aminehumate salts as a binder is that concurrent with its action in buildingup larger pellets and giving greater compression strength, is itsability to burn and thereby enhance the fuel value of coke or any otherfuel used in the firing step. A typical sample of amine humate salt hasa fuel value of 6,00010,000 B.t.u./1b. Therefore the amine humate bindernot only helps to form pellets of requisite size and strength, but alsovola-tilizes in the firing step thereby acting as a minor source of fuelwithout forming any deleterious slag deposits during this particularstep of the process.

As outlined above, in order to promote compactness in adhesiveness ofthe pellets so that they may withstand handling subsequent to theirformation and prior to the firing step, it is necessary that they bemoist and in condition for ready and efficient pellet formation. It isnecessary, then, that water in some form be added to the burden prior tothe pelletization. The added water operates in conjunction with theamine humate salt to give good binding action. In the wet processing ofimpure ores, whereby the desired metal constituent is increased to ausable amount, sufiicient water for good compaction generally remainsafter the completion of this beneficiation. However, in some cases watermay be conveniently added by use of aqueous ore sludge, or may itself beadded at any point in the overall pelletizing process either before orafter the binder has been added to the burden to form a compositethereof.

It is preferred that the aqueous content of the burden prior topelletization comprises 2-20% by weight of water based on the weight ofthe burden. erabl the Water content of the burden forms from 5 to 10% byweight of the entire mixture. In its most favorable aspect a burdencomposition comprises 69% by weight of an aqueous liquid primarilycomposed of water. Whether the above percent weight range is based onthe weight of the burden alone or the composite comprising the burdenand binder is immaterial, due to the relatively insignificant weight ofthe binder in comparison to the burden weight.

The amount of amine humate salt added to the burden may be variedaccording to the particular needs of the pelletizing operation. It hasbeen determined that excellent results are obtained when from 0.1-pounds of amine humate salt per ton of burden are employed. Morepreferably, O.510 pounds of amine humate salt are added per ton ofburden with the most preferable results, from a standpoint ofefiiciency, and cost being obtained in the nange of 0.5-5.0 pounds perton. When measured in terms of parts of binder per million parts ofburden it is preferred that the binder be added in the range of from505000 ppm. and more preferably from 50 to 2500 ppm.

The amine humate salt may be added at any place prior to thepelletization operation. In the normal openating procedure the finelydivided iron ore in any of its various forms and the coke, and, ifnecessary, flux material, which components when combined with the aboverequired amounts of water comp-rise a mixture known as a burden, aremixed together first. The binder may be added in at any spot of theoperation, before, during or after addition of any of the components ofthe burden. It is preferred, however, that the burden be prepared firstand that the binder subsequently be added in required amounts. Partialmixing may be effected by transfer of the burden and binder, but morenearly complete mixing is effected during the balling step itself, inorder to give a fairly "homogeneous iron ore composite.

Any of the many well-known types of pelletizing apparatus may be used inthis operation, but the preferred embodiment involves the use of what isknown as a revolving disc or revolving drum-type pelletiziing machine.In this type of operation the composite comprising the burden andbinders flow over revolving surfaces, and are retained thereon for asufficient amount of time, generally only a few seconds or so, to imparta centrifugal force to the composite and form or ball it into numerousagglomer-ates or pellets. These pellets spinning off the surface of therevolving drum or disc are then caught on a conveyor belt for tnansferto the firing furnace. In the case of revolving discs the surfaces arenormally set at More pref-- 7 an angle of inclination ranging from 40 to60. Additional water may be added to the rotating pelletizing disc inorder to promote better pellet formation.

As mentioned above, the ore-containing materials may also be composed offines, hot or cold, or fine dust. In another embodiment of the inventionthese fines are added to the already formed pellets, and are held incontact with the moist adhesive-type pellets prior to entrance into theignition furnace.

The mechanism by which the amine hnmate salt accomplishes itspelletizing action is not known for certain. However, it is believedthat the binder imparts a degree of adhesiveness to the burden, but evenmore importantly it develops a compressible fluid bond at the particleinterfaces of the burden. Since the binding action is dependent uponformation of thin surface films, rather than upon slurry formations, theamount of necessary moisture comprising a portion of the burden-bindercompo-site will be less than normal, which reduction materially benefitsthe overall efliciency of the pelletizing process. The advantages of theuse of the amine humate binders in the invention are many and varied.For example it was noted in trials, that much larger pellets were formedthan was normal with no binder being applied. In fact,

-the average pellet size was much greater than that resulting from useof prior art binders. Due to the excellent pelletization action, theentire operation was able to be speeded up to a rate considerably abovethat which is considered normal. Also, it was possible to make up theburden to comprise a high amount of flue dust, utilization of which is aconsiderable economic advantage. Prior to invention of the process ofaddition of the amine humate salt compositions of the invention,substantial flue dust content in the burden could not be present withouttending to have adverse elfects on the firing operation.

In addition to the above advantages derived from the use of the bindersof the invention, a further important effect was noted in trials, thatis, increase in compression or green strength of the formed pellets, sothat they were able to withstand handling subsequent to the pelletizingoperation. A high compaction is necessary in order for the pellets toretain their characteristic shape, so that they may be mechanicallyhandled and transferred to the firing furnaces without crumplin-g orcomplete breakdown of pellet formation.- The ability of amine humatepelletizing aids to increase significantly the compressive or greenstrength of the formed pellets will be discussed in more detailhereinafter.

PELLETIZING AIDS The amine humate salts, of course, are the resultantproducts fromreact-ion of a source of humic acid which is a generic termfor acids derived from hum-us or the top layer of the soil containingorganic decomposition products of vegetation etc, with an amine. Sourcesof the humic acid may be from peat, brown coal, lignite, and the like.-Of course, the invention contemplates salts prepared from the above rawmaterials containing varying amounts of humic acid. In fact, it ispreferred that the impure or just mined material be used as a startingreagent due to low cost, availability, and lack of need for costlyprocessing prior to salt formation.

One of the preferred sources of humic acid as used in preparing thepelletizin-g aids of the invention is leonardite, often found inassociation with lignite. This is a specific organic substance namedafter A. G. Leonard who was associated with its discovery. It isconsidered to be more in the nature of a chemical useful in variousadditive processes rather than as a fuel, due to its relatively poorcombustibil-ity and low B.t.u. content per unit weight. Leonardite isprimarily mined from the Harmon bed in Bowman County, North Dakota, andDivide County, North Dakota, and in and around Alpine, Texas. Althoughphysically similar to lignite, leonardite has a much richer oxygencontent than does ligite, ranging in oxygen content from 27-33% byweight, whereas lignite contains about 19-20% oxygen by weight. The highoxygen content of leonardite is ascribed to the presence of carboxylicacid and phenolic groups in the leonardite molecule. Spectral analysishas indicated that leonardite is generically speaking a mixture of humicacids and salts thereof which upon excitation for such analysis, causescertain distinctive spectral patterns to appear. Although not provedconclusively, leonardite is probably a large condensed ring polymericmolecule containing carboxyl groups. The following structural formulahas been proposed as a representative-type molecule defining leonardite.This formula, of course, is not meant to be conclusive but has beentendered in order to show the complex problems in defining such sourcesof humic acid as leonardite, and other humic acid-containing materials.Reference to their mining source is often the most convenient route toprecise definition.

l K n COOII A typical leonardite sample normally said to be comprised ofcalcium, sodium, magnesium, potassium, etc, salts of complex organicacid and free organic acid is partially analyzed as follows: Ash, 14.01;C, 48.75-53.98; H, 3.794.70; N, 1.25; O, 31.99; CH 1.26; CH O, 0.44; CHCO, 0.38.

The equivalent weight of the above sample of leonardite was determinedto be 256.

In order to synthesize the amine humate pelletizing aids of theinvention it is only necessary to add an amino component to the abovehumates. 'Ihe salt-forming reaction is preferably carried out in thepresence of water. A Wide variety of amines may be employed asreactants, but it is greatly preferred that amines be employed whosereaction products with the humus materials be watersoluble orwater-dispersible. For best elfectiveness the amine humate salts musthave the ability to be solubilized, or at least must have suificienthydrophilic character to be colloidally dispersed in water. Among thosepreferred amines are m-onoamines, and more preferably amines con tainingat least one lhydroxyl group. Amines which have been employed with muchsuccess include methyl amine, ethyl amine, diethyl amine, morpholine,butyl amine, isopropylarnine, d-i-isopropylamine, N-methyl morpholine,triethylamine, aminoethyl ethanolamine, diethanolamine, diethylethanolamine, di-isopropanolamine, dimethyl ethanolamine, dimethylisopropanolamine, N-hydroxy ethyl morpholine, N-methyldiethanolamine,monoethanolamine, monoisopropanolamine, triet-hanolamine,tri-isopropanolamine, 1,1-dihydroxymethyl ethylamine,1,1-dihydroxymethyl n-propylarnine and polyglycolamine. A preferredspecies of the last amine listed has a general formula, H NCH CH (OCH CH),,OH where n may vary from 1 to 10.

The method of preparation of amine salts by reaction of the respectivesalt-forming ingredients may be considerably varied. A representativemethod is to dissolve the amines in water, mix thoroughly with theleonardite, and then allow the salts to air-dry from the liquid media.The drying step may also be conveniently carried out in drying ovens.The resultant salt is then broken up somewhat and is immediately readyfor pelletizing use. The mode of addition of reactants to water or toeach other is immaterial. For example, the humus material may be firstdispersed in Water and the amine added thereto. Likewise, an aqueous.amine solution may be prepared, to which is added the humic acidmaterial. During the reaction the basic amine groups react with thecarboxyl groups existing on the humic acid, in order to to-rm saltshaving requisite water solubility.

In preparation of the above amine humate salts, it is preferred thatfrom 0.1 to 1.0 equivalent of amine be used for each equivalent of humicacid. The equivalent weight of the particular humic aoid materialemployed is the weight required to react with one mole of sodiumhydroxide, depending in turn upon the number of reactive groupsavailable.

If desired, the above salt forming reaction may be carried out either atroom temperature or at elevated temperatures. The amount of timenecessary to etfect the reaction is quite minimal and usually reactionis considered complete in times varying from 2-60 minutes.

An embodiment of the invention also includes the use of both aminehumates and alkali metal or ammonium humate salts in combination. Whilethe amine humate salts are clearly superior to the alkali metal orammonium humate salts, in some instances it may be preferable to employa combination of the two in order to lower the total cost of treatment.One expedient of this combination is to form separately the amine humatesalts and alkali metal or ammonium humate salts and then combine therespective ingredients in one composition. It is preferred that such acomposite contain at least by weight of amine humate salt and morepreferably from 20 to 80%. In another expedient the same source of humicacid may be first treated with alkali metal, alkaline earth metal or anammonium base such as ammonium hydroxide and then treated further with asource of any one or more amines as represented above. Likewise, thehumic acid material may be first treated with an amine and then reactedsubsequently with the alkali metal, alkaline earth metal or ammonium.

The inorganic metal salts of the humic acid material, and preferablysodium leonardite, when used in combination with the amine humate saltsas leonardite amine salts, achieve best results when the inorganic humicsalt has been prepared by reaction of humic acid material with ammoniumhydroxide or an alkali metal or alkaline earth metal hydroxide, such assodium hydroxide, calcium hydroxide, magnesium hydroxide, or potassiumhydroxide in order to give a product which has a pH greater than 7.0,measured as a 10% dispersion in water. Preferably samples of humic acidsuch as leonardite give better results as a binding agent in combinationwith the amine humate salts when they have pHs as a 10% aqueoussolution, of between 8 and 12. Most preferably inorganic humate saltssuch as leonardite salts having a pH greater than 9.0 are employed inthe pelletizing operation when used as one of the components in acomposite with the amine hum-ate salts or amine salts of leonardite. Itis believed that the more highly basic humic salt material has betterdispersibility and mixing tendencies when added to the moist burden.

10 The following examples below illustrate the typical methods ofpreparing the amine humate salts of the invention:

Exampe I 32 grams (0.27 equivalent) of tris (hyroxymethyl) methyl aminewere dissolved in 50 mls. of water. This solution was then mixed withgrams of leonardite humic acid (0.4 equivalent). The resultant mixturewas then agitated until no further evolution of heat was noted from thesalt forming reaction. After cooling, the salt product was driedovernight in the open atmosphere and then pulverized. This amine humatesalt had a moisture content of 8.4%. The above product was designated asComposition A.

Example 11 This preparation followed the procedure outlined generally inExample I, with the exception that 20 grams of triethanol amine wasemployed as the amine reactant. The final product had a moisture contentof 12.1%. This product was designated as Composition B.

Example 111 In this example the procedure of Example I was followed withthe exception that 30 grams of triethanolamine were employed as theneutralizing base. The product was labeled Composition C.

In order to determine the efiicacy of the invention, the amine humatesalt pelletizing aids were tested for their utility in producing thelarge size desired pellets, and particularly for ability to impart tothe formed pellets the essential character of green strength or pelletstrength before firing. Without sufiicient green strength the formedpellet tends to crump or disintegrate partially or wholly before beingfused. Thus only pellets of inferior quality are formed. The test unitemployed to pelletize a burden was a rotating disc pelletizer. The discwas fitted with a 4 sleeve allowing burden charges up to 5 pounds inweight to be placed on the disc without spillage. The particular burdenpelletized in this case was taconite ore which had been previouslybeneficiated by means of a magnetic separation until iron content ofapproximately 60-70% was reached. The burden had a moisture content ofbetween 8 and 10%. :Five pounds of burden were placed on the disc panalong with the binder to be tested and rotated for 3 minutes. Theagglomerate was then removed and sieved through a series of screens todeter- \mine the size distribution. The 4 mesh size pills were then alsotested for green strength by a simple test described in detail below.

Compositions A, B and C, were added to the above burden in order to givea binder addition calculated as 5 pounds per ton of burden. Also a blankwithout any additive was run, as well as a run involving the use of 16pounds per ton of bentonitic clay, a well-known commercial binder usedto agglomerate many ore materials. Table I below shows that the aminehumate salt pelletizing aids showed considerably greater activity inpromoting the production of the desired large size pellets, whencompared to the blank and even in relation to the known bentonite claypelletizing aid. Its effectiveness when compared to that of bentonite isparticularly striking in view of the fact that the amine humate salt isused at an additive dosage of less than /3 that of bentonite. The aminehumate salts produced a higher number of pellets and pellets which arescreened through the relatively large size sieves, for example throughseries having mesh sizes of 4 (0.187") 5, and 7, etc. Use of thebentonite clay as an agglomerating agent resulted in a high percent offines or material being screened through a 20+ mesh size screen, thatis, one allowing a screening only of those particles less than 0.0331"in diameter. Other tests involving bentonite yielded as high as 30%fines. The larger sized pellets of course are desired, and give mostefficient results as blast furnace feed after filsion. vOn the otherhand, fines or micro-pellets have a tendency to be blown through thefiue and lost, or must be subsequently recovered and reagglomerated.

In order to determine the very essential property of green strength, thepellets treated with the above agglomerating agents and the blankmaterial which was retained in the 4 mesh size screen, were thenevaluated by means of a Drop Test. This test consists of dropping these4 mesh pellets from both 18 and 36 inch heights upon a hard surface. At18" a total of 20 pills were dropped up to three times each, dependingupon when each breaks. A score of 3, 2 and 1 respectively is assigned toeach pill, corresponding to the number of drops each survives. A perfectscore then is 60. For the 36" drop test, a test with no cracks isassigned 1, a cracked but not broken pill 0.5; and for those pelletswhich break. A perfect score in this case then is 20. The latter 36 testis particularly meaningful in determining which pellets have thenecessary green strength to withstand the handling subsequent topelletizing prior to the fusing process. Not only must pills ofsufficient diameter be produced, but also these pellets must be able tomaintain their integral character without breakdown or crumpling. Thedrop test and particularly the 36" drop tests are excellent criteria indetermining the strength or ability to maintain formed integralcharacter.

Table II below shows that the taconite burden when pelletized throughthe aid of the amine humate salts formed excellent pellets having greenstrength or compression strengths heretofore unobtainable using priorart aids. In particular, those pellets agglomerated in conjunction withthe amine humate salts of the invention scored high in the stringent 36"drop test. All of the amine humate salts of the invention showed clearlysuperior activity in promoting green strengths of pellets formedtherewith, over those corresponding size pellets formed through the aidof bentonite or formed without aid of any treatment whatsoever. Thus,even though the pill size distribution obtained with no additiveappeared passable, the subsequent low strength of such untreated pelletsdemonstrates the need for pelletizing. This need was not satisfiedthrough use of the bentonite material, which not only resulted in alarge amount of fines when employed, but the formed pellets wereextremely soft when compared to like sized pellets formed through theaid of amine humate salts.

Sodium salts of leonardite were also synthesized and used as pelletizingaids. The size distribution and strength of the pellets were likewiseevaluated, and while the sodium salts of leonardite gave excellentactivity in comparison to the blank and even considerably greaterpelletizing activity when compared to the bentonite material,

these salts did not measure up to the high degree of efficiency as shownby the amine leonardite salts. However, various combinations of alkalimetal humates such as the sodium salt of leonardite and Compositions A,B and C, showed nearly as efilcient pelletizing activity as did theamine salts alone.

We claim as our invention:

1. In a method of producing improved metallic mineral pellets whichcomprises the steps of comminution of a mineral ore to particulatestate, concentrating the valued mineral constituent thereof to anincreased purity, treating said mineral to obtain a wetted particulatemass, pelletizing said mass to form integral units and firing saidformed pellet units to a hardened state; the improvement which comprisesthe step of adding to said wetted mass prior to pelletization at least abinding amount of an amine humate salt whereupon pellets are producedhaving increased strength and cohesiveness.

2. The method of claim 1 wherein said amine humate salt is an amine saltof leonardite.

3. The method of claim 2 wherein said amine humate salt is anhydroxyamine salt of leonardite.

4. The method of producing improved metallic mineral pellets ofincreased strength and cohesiveness which comprises the steps of addingat least a binding amount of an amine humate salt to a wetted mass of acomminuted metallic mineral to form a composite and pelletizing saidcomposite to form integral units thereof.

5. The method of claim 4 where said amine humate salt is an amine saltof leonardite.

6. The method of claim 5 wherein said amine humate salt is an hydroxyamine salt of leonardite.

7. The method of claim 4 wherein said wetted particulate mass comprisesfinely divided iron ore.

8. The method of claim 4 wherein said wetted particulate mass comprisesfinely divided iron ore and iron dust added thereto.

9. The method of claim 4 wherein said units are fired to a hardenedfixed condition while maintaining their integral character.

10. A metallic mineral pellet having improved green strength andcohesive character which comprises a major portion of a metallic mineraland a minor portion of a binder comprising an amine humate salt.

11. The pellet of claim 10 wherein said amine humate salt is an aminesalt of leonardite.

12. The pellet of claim 11 wherein said amine humate salt is an hydroxyamine salt of leonardite.

13. The pellet of claim 8 wherein said metallic mineral comprises irondust.

14. The pellet of claim 10 wherein said binder is present in an amountvarying from -5000 p.p.m. and said mineral is taconite.

15. As a pelletizing aid an amine humate salt.

16. The composition of claim 15 wherein the said salt is an amine saltof leonardite.

17. The composition of claim 15 wherein said salt is an hydroxy aminesalt of leonardite.

18. In a method of producing improved metallic mineral pellets whichcomprises the steps of comminution of a mineral ore to particulatestate, concentrating the valued mineral constitutent thereof to anincreased purity, treating said mineral to obtain a wetted particulatemass, pelletizing said mass to form integral units, firing said formedpellet units to a hardened state, heating said units to a liquid massand cooling said liquid mass in molds whereby metal ingots are formed;the improvement which comprises the step of adding to said wetted massprior to pelletization at least a binding amount of an amine humate saltwhereupon pellets are produced having increased strength andcohesiveness.

19. The method of claim 18 wherein said amine humate salt is an aminesalt of leonardite.

(References on following page) References Cited by the Examiner UNITEDSTATES PATENTS Stillman 75-3 Rawlins et a1. 260501 De John 75-3 Cooper 755 De Vaney 7 5-5 14 2,992,093 7/1961 Burdick 2605 15 3,030,412 4/ 1962Higuchi et a1 2605 15 3,149,958 9/1964 Ward 75-5 OTHER REFERENCESLeonardite: A Lignite Byproduct, RI5611 Bureau of Mines Investigations(1960), 12 pages.

BENJAMIN HENKIN, Primary Examiner.

1. IN A METHOD OF PRODUCING IMPROVED METALLIC MINERAL PELLETS WHICHCOMPRISES THE STEPS OF COMMUNICATION OF A MINERAL ORE TO PARTICULATESTATE, CONCENTRATING THE VALUED MINERAL CONSTITUENT THEREOF TO ANINCREASED PURITY, TREATING SAID MINERAL TO OBTAIN A WETTED PARTICULATEMASS, PELLETIZING SAID MASS TO FORM INTERGRAL UNITS AND FIRING SAIDFORMED PELLET UNITS TO A HARDENED STATE; THE IMPROVEMENT WHICH COMPRISESTHE STEPS OF ADDING TO SAID WETTED MASS PRIOR TO PELLETIZATION AT LEASTA BINDING AMOUNT OF AN AMINE HUMATE SALT WHEREUPON PELLETS ARE PRODUCEDHAVING INCREASED STRENGTH AND COHESIVENESS.